A person who has spoken with Cotton told the Associated Press that the Republican congressman will announce his candidacy at an event Tuesday in his hometown of Dardenelle.

Pryor, who is seeking a third term, is considered one of the most vulnerable Democrats in 2014 and Arkansas is one of several states that will play a role in deciding who holds power in the Senate.

President Obama is deeply unpopular in Arkansas and Pryor has been assailed by conservative groups for voting for the national health care law and the government bailout of banks.

Cotton, 36, went to Harvard Law School and served in the U.S. Army in Iraq and Afghanistan. He was elected to a seat previously held by a Democrat. In his short time in Washington, Cotton is considered part of a group of younger conservatives willing to challenge the GOP leadership.

He's gotten national media attention, which is unusual for a newcomer to Congress, and has already appeared on the NBC"s Meet the Press to discuss national security and foreign policy. Cotton recently told USA TODAY's Susan Page that the Senate approach to rewriting immigration laws won't work in the GOP-controlled House.

Justin Barasky, a spokesman for the Democratic Senatorial Campaign Committee, criticized Cotton for wanting to make the jump to the Senate after only seven months in Congress and called him an "extreme ideologue."

"Tom Cotton begging for a promotion to the U.S. Senate on the same day he's going to vote to put the screws to Arkansas families by making college less affordable is exactly the kind of arrogance and poor judgment we've come to expect from this guy," Barasky said, referring to an upcoming vote on college loan rates. "Cotton votes in lock step with Washington special interests and against Arkansas, but still thinks that he deserves a promotion."

While Pryor's votes supporting President Obama's policies will be heavily scrutinized in the campaign, the senator often says that he listens first to the voters of Arkansas. Pryor bucked Obama, for example, by voting against the proposal to expand background checks on gun buyers - an issue that is deeply felt in Arkansas - and is one of the few remaining Democrats in the Senate to oppose gay marriage.

Pryor had $3.9 million in his campaign account at the end of June. Former President Bill Clinton, a longtime friend of the Pryor family, has already helped the senator raise money and could be called on again for support during the campaign.